Coach Jim Harbaugh expressed optimism Thursday that last season's two top performers, linebacker NaVorro Bowman and wide receiver Anquan Boldin, will be back next season.

Bowman had surgery this month to repair the serious knee injury he sustained in the NFC Championship game. Boldin is a free agent.

Speaking from Indianapolis, where the NFL scouting combine begins Saturday, Harbaugh said he doesn't expect Bowman to be ready for the season opener.

"Halfway through the season (or) something like that would be more realistic," Harbaugh said in a team release.

Bowman led the 49ers in tackles for a third straight season and won their prestigious Len Eshmont Award in a vote by his teammates.

As for Boldin, voted by coaches as team MVP last season, negotiations for a new contract are underway.

"The direction it's going is very positive because we're unanimous," Harbaugh said. "It's not just me who wants Anquan Boldin back. It could be days, weeks, but there's a process, and it's going in a positive direction."

In other news:

- Defensive tackle Tank Carradine, who did not play his rookie season, is looking solid after having scar tissue removed from his surgically repaired right knee, Harbaugh said.

- Eric Mangini, a senior offensive consultant last season, will take over as tight ends coach in place of Reggie Davis, who has become the assistant offensive line coach.

- Wide receiver Jon Baldwin has reduced his nonguaranteed base salary from $1.4 million to $645,000, ESPN first reported. He had three catches in just seven games after the 49ers acquired him from the Kansas City Chiefs in August for 2012 draft bust wide receiver A.J. Jenkins.

- General manager Trent Baalke is scheduled to address the media Friday morning (7:30 a.m., PT) at the combine. Baalke has not publicly spoken since the 49ers lost in the NFC Championship game to eventual Super Bowl champion Seattle.